Contribution of sex and cellular context in the regulation of brain corticosteroid receptors following restraint stress

The two subtypes of corticosterone receptors in the rat brain play a pivotal role in the modulation of the stress response. Appropriate control of their gene expression is therefore critical for the maintenance of cellular and organism homeostasis. In this study, we investigated the contribution of gender and of the cellular environment of certain brain areas to the expression of both types of corticosteroid receptors, following restraint stress. Adult Wistar rats of both sexes were subjected to acute, chronic or to a combined chronic plus acute stress regimen, and the expression of glucocorticoid and mineralocorticoid receptors was evaluated in their hippocampus, hypothalamus, pituitary and frontal cortex, by using Northern blot analysis. Significant sex differences were observed in the first three brain areas examined as to the stress-induced expression of corticosteroid receptors. Among these, females showed a distinct mechanism of regulating glucocorticoid/mineralocorticoid receptor ratio in the hippocampus upon chronic stress, while the female hypothalamus was more prone than the male to changing corticosteroid receptor expression in response to restraint stress. In another set of experiments, we assessed the influence of ovarian steroids on stress-induced corticosteroid receptor expression in the above brain areas by analyzing ovariectomized rats exposed to short-term restraint. Our results showed that although,ovarian steroids affect the stress-induced expression of receptor genes in a region-specific manner, their elimination does not appear to lead to the male pattern of expression. These findings provide further evidence for the existence of both regional and gender specificity in the regulation of brain and pituitary corticosteroid receptors following stress, and support the hypothesis of a distinct male and female neuroendocrine axis in response to stress. Copyright (C) 2000 S. Karger AG, Basel.